Well I,ve did all the Ultimate TBI mods and the cars running again(still having the RF brake lock up problem though). I'm going to try to adjust the fuel pressure. I've got a 60# TBI fuel pressure guage, but this only tells the fuel pressure thats getting to the TBI regulator, right? I'm running a Holley Blue Pump, I've got a regulator that came with the pump but I'm not using it right now. What should be the least amount of pressure be and also what is too much? If need be I can get a different spring for the Holley pump to raise the pressure up 18#'s or use the regulator that came with it to lower it.

About the adjusting of the fuel pressure via the O2 sensor. I only read the voltage at WOT going down the road,right? Should I also get the 60# TBI fuel pressure guage in a place that I can see it at WOT? If so around what pressure should it be at WOT?

Right now it seems like it may have to much pressure, the fuel sprays out real hard. The fuel cone coming out of the injector looks like it is too wide for the throttle bores and it bouneses back up off the throttle blades. By the way I'm running two injector pod gaskets and I removed the ridge around the throttle bores.

Do any of you think I'd be better off with an vacume adjustable fuel pressure regulator? I've seen some people on here with them and read several posts about them but still don't know if one would help me or not. Thanks for any info ya can give me on this, Bobby

 

Come on no one has any tips on this? Nearlly everone on here is allways talking about doing this stuff, wheres all the comments and opinions and people raging you when you need them?

 

With the present mods, id jsut leave it around the stock pressure, which is around 9-12 psi. I wouldnt go much above that untill you have a combo that needs the extra fuel flow. Same thing with the VAFPR. That will come in handy when the engines volumetric efficiencies shift higher up into the rpm band and you have to run a large injector and need more fuel and still desire good idle and p/t caricteristics.

 

oh, ideally you want to have the fuel it just above the butterflies so its sheared into a fine mist by the airflow around the butterflies. If it hits the butterflies themselves itll just roll of the rear when the throttle is opened, causing the rear cylinders to be richer then those in the front.

 

The pressure should be where it gives you best performance. Not some reading on a gauge or some 02 reading.

You don't race 02 readings or gauges.

Measure performance. This means trap speeds, dyno, gtech etc.

 

Make sure you have the ability to data log and monitor the computers blms if you decide to start tinkering with the fuel pressure. The commanded WOT air fuel ratio is a bit rich in the ecm and what gives the best performance at WOT may leave the blms a tad high at p/t. On my 88 the ecm for that year actually adjusted the blms at WOT to get the desired AFR and it would fight me when I went to adjust the fuel pressure. Get a scantool or winaldl so you can see the whole picture. Try to balance the WOT and part throttle fueling to get teh best overall performance.

 

How will I know when I'm at the stock pressure(9-13psi)? I took the TBI regulator apart to make it adjustable and now just want to set it to where it should be. My fuel pressure guage hooks up before the TBI regulator so how do I know the fuel pressure at the injectors?. As far as adjusting by the O2 sensor, I was just going by the Ultimate TBI pages in the Tech section, should these be disreguarded?

I've got the little pin that stickes out of the TBI regulator about 1/4 of the way up from the bottom now. Does this sound right? I'll hook the TBI fuel pressure guage up lator and get back with my readings and maybe ya can help me more then as I will have more info. Thanks, Bobby

 

as long as the gauge is hooked to the inlet side (larger 3/8 line) of the fuel system itll show what the pressure is at the injectors.

 

Well I hooked up the TBI fuel pressure guage and I'm getting 12# idling and when I rev on it real hard it will drop to just before 11#s. Is this good or what?

You know where the metal fuel lines come up from the tank on the drivers side and theres the two short rubber lines that run over to the engine,yea. Well this is where I've got the Holley Blue Pump hooked up, pulling fuel from the tank. I put the tee for the fuel pressure after the pump where the rubber line goes back into the steel line on the motor.

dimented24x7,
How does it show the pressure for the injectors when theres still a regulator between the fuel guage and the injectors? If I turn the regulator up or down will the guage still show it?

I also set the timing while I had it running. I set it at 4*BTDC. I think 0* is stock, right? It does seem to be running smother than it ever did before. It seems like when you goose on it it turns up a lot quicker, but it had setup about 2 years so I don't really remember.

 

 

12psi sounds like a good fuel pressure for you, going of of what we know. I am not too familiar with the holley blue pump, but I assume it's an inline pump. As long as you have the pressure gaude hooked up after the pump in the feed line, you are good to go, as that is the pressure going to the injectors.

It is common for there to be a little surge in pressure when under load at first. Your best way of telling if everything is good as far as fp is concerned is to monitor the fp while driving the car at WOT. I tape my guage to the windshield.

Basically, the regulator controls the pressure from the pump to the injectors, so basically the whole fuel line. Adjusting the regulator will yeild a change shown on the pressure gauge.

 

r90camarors,
Heres a link to info on the Holley Blue Pump: http://www.holley.com/HiOctn/ProdLin.../12-802-1.html
Also do you think I need to try adjusting the pressure by the O2 sensor as in the Ultimate TBI write up in the tech section? Thanks, Bobby

 

As far as O2 sensor readings go, it is kinda tough to say. The narrow bands in our cars are pretty much only good when the a/f ratio is 14.7. Anything higher or lower and it starts to lose accuracy. And on top of things, if you are using winaldl to find the o2 readings, then you have to deal with the slow baud rate of our ecms, in that it only logs once every 1.1-1.2 seconds. Don't get me wrong, I do it when I need to to get a rough idea.

That is where the wideband comes into play. Much more accurate. There is a nice article on the Innovate WB O2 in this months (Feb) Car Craft. Definetely check it out, it helped me understand how they work.

If this is not an option, then using trap speeds is the next best option, even if it is a g-tech.

 

Yea, I just ordered a G-Tech, it should be here any day. I'm getting a 3-wire O2 sensor conversion kit from http://www.howell-efi.com
Thats the same company that I got the 700cfm Holley 4bbl TBI from. I wish I could figure out how to wire up a 4-wire O2sensor, seeing how I've got 2 of them that I took off my "97 Z28(they're the after cat conv O2 sensors). Guess I'll have to go get the Feb. Car Craft issue, I uselly read Chevy High Performance but I've been wanting to check them out since CHP's editor went over there to work. I'll keep the progress posted. Thanks, Bobby